The present invention relates to an apparatus for kinesthetic signaling to the driver of a motor vehicle utilized, for example, in the context of an adaptive vehicle speed control system or spacing control system of a motor vehicle, which is also known as Adaptive Cruise Control (ACC).
The term xe2x80x9ckinestheticxe2x80x9d derives from a Greek word, and is to be understood in the sense that the driver experiences bodily movements.
The paper xe2x80x9cAdaptive Cruise Controlxe2x80x94System Aspects and Development Trendsxe2x80x9d by Winner, Witte et al., presented as SAE Technical Paper Series No. 961010 at SAE, Feb. 26-29, 1996, describes a system for controlling the speed and/or spacing of a motor vehicle. An ACC system as described in the paper is capable of influencing the speed of the motor vehicle. One of the possibilities for doing so is by way of an active braking intervention. In this context, the maximum attainable braking effect is limited to a maximum value. In the event that this braking effect is not sufficient, for example, to come to a stop at a safe distance behind a preceding vehicle, it is necessary for the driver to be made aware of this situation. This can be done, for example, by way of an acoustic signal via a loudspeaker. German Patent No. 33 04 620 describes a device for maintaining a constant driving speed for motor vehicles. The device includes, inter alia, a detector that ascertains the spacing between the vehicle and a vehicle located in front of it, as well as a control system with which a suitable intervehicle spacing is determined. With this device, the vehicle speed resulting from the suitable intervehicle spacing is controlled primarily via a throttle valve displacement. In the event the throttle valve displacement alone is no longer sufficient to establish the desired vehicle speed or the desired intervehicle spacing, on the one hand a warning device is provided that prompts the driver to actuate the brakes or to steer around the preceding vehicle. On the other hand, in accordance with a further exemplary embodiment, provision is made for the control system to actuate the brake automatically.
German Patent No. 43 40 467 describes a hydraulic vehicle braking system, operating with external force, that makes it possible to transfer a desired brake pressure setpoint to the vehicle braking system, which controls the braking force in accordance with this definition.
European Patent No. 0 348 691 describes a method and an apparatus corresponding thereto for haptic indication of the spacing warning in a motor vehicle. In this context, if the spacing of the motor vehicle falls below a minimum value in both the forward and the rearward direction, a haptic indication is produced by vibrating the steering wheel, the driver""s seat, or the entire passenger compartment. Vibration of the passenger compartment is made possible, inter alia, by activating the brakes or by acting on the brakes. This action makes it possible to produce vibrations at differing intensity and with different profiles, so that multi-stage spacing warnings can be transmitted to the driver.
German Patent No. 195 44 923 describes an apparatus and a method for vehicle control that informs the driver when a maximum braking force permitted by the vehicle control system is being applied, so that the driver can make the decision as to whether to take over control of the vehicle from the vehicle control system. In this context, a deceleration requirement is determined in an adder device in accordance with data supplied by a distance sensor. This deceleration requirement signal is applied to the input of a comparator, which determines whether the deceleration requirement is greater than the maximum deceleration achievable by the controller of the vehicle control system. If so, the comparator activates an information driver element. This element is connected to a flashing light, a sound generator, and a haptic control element. With the latter, the driver is informed by touch.
The conventional sensor systems generally do not make it possible to use ACC at very low speeds, since they do not have sufficient detection coverage in the close-in range. In order to prevent improper operation, the ACC function is shut down at low speeds.
Often, it is precisely the deceleration of the preceding vehicle that causes the speed to fall below the shutdown threshold. It is necessary in this case as well for the driver to be clearly and unequivocally made aware that the ACC system is not functioning.
Further reasons for shutting down the ACC without driver deactivation may include faults detected by the ACC system (including all necessary subsystems), or the risk of overheating the brakes.
An object of the present invention is to create a reliable signaling system for the driver of a motor vehicle in the context of systems that relate to longitudinal control of the motor vehicle.